Drying arrangement on machines for coating supporting webs, more especially with photographic emulsions

ABSTRACT

A web coated with a photographic emulsion is supported for drying in a blast of hot air on spaced sets of two-roll hollow suction devices. A suction box having an arcuately pointed section disposed closely adjacent and between the peripheries of the rollers on the side opposite the web lowers the pressure between the web and the rollers to increase the force and area of rotation-inducing contact between the web and the rollers and to firmly guide and retain the web on the rollers irregardless of its orientation. This minimizes the number of rollers needed to support the web to increase the area of contact with the hot air and facilitating drying.

United States Patent 1 [1 1 3,738,018 Herzhoff et al. [4 June 12, 1973[54] DRYING ARRANGEMENT ON MACHINES 3,065,098 11/1962 Brooks 34/23 X FORCOATING SUPPORTING WEBS, MORE ESPECIALLY WITH PHOTOGRAPHIC EMULSIONSInventors: Peter Herzhoff; Hans Gref; Wolfgang Schweieher; MaxHeidenreich; Hans Frenken, all of Leverkusen, Germany AGFA-GevaertAktiengesellschaft, Leverkusen, Germany Filed: Apr. 5, 1972 Appl. No.:241,223

Related U.S. Application Data Continuation of Ser. No. 861,412, Sept.26, 1969, abandoned.

Assignee:

References Cited UNITED STATES PATENTS 10/1940 Haas 34/157 X PrimaryExaminerMeyer Perlin Assistant ExaminerRonald C. CaposselaAttorney-Connolly and l-lutz [57] ABSTRACT A web coated with aphotographic emulsion is supported for drying in a blast of hot air onspaced sets of two-roll hollow suction devices. A suction box having anarcuately pointed section disposed closely adjacent and between theperipheries of the rollers on the side opposite the web lowers thepressure between the web and the rollers to increase the force and areaof rotation-inducing contact between the web and the rollers and tofirmly guide and retain the web on the rollers irregardless ofitsorientation. This minimizes the number of rollers needed to support theweb to increase the area of contact with the hot air and facilitatingdrying.

4 Claims, 3 Drawing Figures DRYING ARRANGEMENT ON MACHINES FOR COATINGSUPPORTING WEBS, MORE ESPECIALLY WITII PHOTOGRAPIIIC EMULSIONS This is acontinuation of application Ser. No. 861,412, filed Sept. 26, 1969, nowabandoned.

This invention relates to a drying arrangement for machines for coatingsupporting webs, more especially with photographic emulsions. Thearrangement comprises a duct in which the supporting web is guided overrotatable cylinders. These cylinders are set in rotation by thesupporting web, which is advanced by separate feeding devices.

It is a known condition in connection with the construction of suchcylinder or roller paths that a minimum wrapping angle has to bemaintained for each cylinder. Relative speeds between the web andcylinder surface are avoided by this means. This is especially importantwith material sensitive to scratching, particu larly photographic films.

The wrapping angle is just as significant with absorbent supports suchas photographic papers which are coated on one side in the coatingmachine. Moistening on one side of the support leads to the known upwardcurling of the edges of the web, and the consequences of this curling,namely the bending over of the edges and cracking of the web. This canbe avoided if wellwrapped guide rollers are arranged at not too largeintervals, the web always being straightened again on said rollers.

The known arcuate drying paths, e.g., the spiral web guidingarrangement, correspond to this condition. Modern developments, however,have resulted in socalled flat driers, in which the cylinder axes lie inone plane. These driers, which are of very simple construction, can bemade of any desired length.

With a strong nozzle blowing section on one side, it is possible in aflat drier to obtain a sufficient wrapping for driving the cylinders bysuitable matching of the impact pressure to the web surface and webtension. This is provided the bearing friction of the cylinders is keptlow. The reliability of such a construction for the production ofphotographic films sensitive to scratching does, however, leave much tobe desired. With paper coated on one side, however, this wrapping anglecaused by the impact pressure is insufficient in order to counteract theaforementioned difficulties at the edges of the web.

One known web-guiding element is the hollow suction device, with whichthe web is guided over a succession of rollers disposed closely adjacentone another, a vacuum being applied between the rollers, so that the webruns in undulated form over the roller path. A good wrapping angle is inthis case provided for each roller. It is, however, too costly to equipan entire flat drier throughout its length with a hollow suction device.Furthermore, a considerable portion of the back of the web would becovered by the rollers and consequently the drying of the back, which isnot to be neglected with an absorbent support, is undesirably impaired.

It has now been found that the disadvantages of known dryingarrangements can be avoided by the web being guided at prescribedintervals over two-roller hollow suction devices. The result therebyachieved is that the web can be guided through a flat drier of anydesired length without involving heavy expense in construction orinstallation costs. Several flat driers equipped with two-roll hollowsuction devices can in addition be connected in seriesin a manner knownper se into a space-saving duct drier with loop-shaped guiding of theweb. The deflection of the web into the next flat drier section is inthis case always effected over air cushions with deflection of the layerside, so as to avoid damage, while the deflection of the web on the sideop posite to the layer or coating takes place over rollers.

One embodiment of the drying arrangement according to the invention isnow to be explained more fully by reference to a drawing, wherein:

FIG. 1 shows the two-roll hollow suction device in longitudinal section;

FIG. 2 shows it in cross-section; and

FIG. 3 shows a diagrammatic construction of the drying arrangement witha loop-like guiding of the web.

In FIGS. 1 and 2, a supporting web 1 coated with photographic emulsionruns over a pair of cylinders or rollers 2 and 3, which in conjunctionwith a suction box 4 and a suction pipe 5 form the two-roll hollowsuction device 6. Suction box 4 has an arcuately pointed sectiondisposed between and closely adjacent the peripheries of rollers 2 and3. The rollers 2 and 3 are mounted with their journals 7 and 8 in theside members 9 and 10 of the suction box 4. Under the influence of thesuction effect, the supporting web 1 wraps around the two rollers at anangle a.

In FIG. 3, the web 1 is guided over a number of tworoll hollow suctiondevices 6, air cushion guiding arrangements 11 being provided at thedeflection points on the coating side. At the other deflection points,where the coating is outermost, the web 1 is guided over guide rollers12. The walls of the channel or duct are omitted from the Figure for thesake of clarity.

We claim:

1. In a drying arrangement for coated webs being transported in asubstantially linear path more especially coated with photographicemulsions, the arrangement comprising means for guiding and retainingthe web upon,rotatable rollers, wherein at predetermined spacedintervals two-roll hollow suction devices are disposed in contact withsaid web for guiding and retaining it, said two-roll hollow suctiondevices eachcomprising a pair of freely rotatable cylindrical rollershaving parallel axes and peripheries disposed closely adjacent eachother, a suction box disposed closely adjacent and between theperipheries of said rollers on the side opposite said web and having anarcuately pointed section disposed centrally between and closelyadjacent said peripheries of said rollers whereby the static airpressure between said peripheries is reduced below atmospheric pressureand the area of forceful contact of said web with said rollers isincreased by the suction effect resulting from the differential betweenatmospheric pressure on the portion of said web remote from said rollersand the reduced pressure on the portion of said web between theperipheries of said rollers to pull said webs in firm rotation-inducingcontact with said rollers irrespective of the weight of the web in ashallow curved indentation from said substantially linear path into thespace between said rollers whereby said web is firmly guided andretained in said substantially linear path irregardless of itsorientation.

2. A roller support as set forth in claim 1 wherein side members areattached to the sides of said suction box adjacent the ends of saidrollers, and bearing and journal means rotatably connect -the ends ofsaid rollers wish said side members.

3. A roller guide and retainer for an arrangement for drying webscomprising a pair of cylindrical rollers freely rotatably mounted inparallel axes with their peripheries disposed closely adjacent eachother, a suction box disposed closely adjacent and between one side ofsaid peripheries and having an arcuately pointed section disposedcentrally between and closely adjacent said peripheries of said rollers,a web disposed in contact with said rollers on the side opposite fromsaid suction box, a conduit connected to said suction box for exhausingair from it whereby the static air pressure between said peripheries andsaid web is reduced to increase the forceful contact between saidsupporting web and said peripheries of said rollers as a result of thedifferential between atmospheric pressure on the portion of said webremote from said rollers and the reduced pressure on the portion of saidweb between the peripheries of said rollers to pull said webs in firmrotationinducing contact with said rollers irrespective of with saidside members.

1. In a drying arrangement for coated webs being transported in asubstantially linear path more especially coated with photographicemulsions, the arrangement comprising means for guiding and retainingthe web upon rotatable rollers, wherein at predetermined spacedintervals two-roll hollow suction devices are disposed in contact withsaid web for guiding and retaining it, said two-roll hollow suctiondevices each comprising a pair of freely rotatable cylindrical rollershaving parallel axes and peripheries disposed closely adjacent eachother, a suction box disposed closely adjacent and between theperipheries of said rollers on the side opposite said web and having anarcuately pointed section disposed centrally between and closelyadjacent said peripheries of said rollers whereby the static airpressure between said peripheries is reduced below atmospheric pressureand the area of forceful contact of said web with said rollers isincreased by the suction effect resulting from the differential betweenatmospheric pressure on the portion of said web remote from said rollersand the reduced pressure on the portion of said web between theperipheries of said rollers to pull said webs in firm rotation-inducingcontact with said rollers irrespective of the weight of the web in ashallow curved indentation from said substantially linear path into thespace between said rollers whereby said web is firmly guided andretained in said substantially linear path irregardless of itsorientation.
 2. A roller support as set forth in claim 1 wherein sidemembers are attached to the sides of said suction box adjacent the endsof said rollers, and bearing and journal means rotatably connect theends of said rollers wish said side members.
 3. A roller guide andretainer for an arrangement for drying webs comprising a pair ofcylindrical rollers freely rotatably mounted in parallel axes with theirperipheries disposed closely adjacent each other, a suction box disposedclosely adjacent and between one side of said peripheries and having anarcuately pointed section disposed centrally between and closelyadjacent said peripheries of said rollers, a web disposed in contactwith said rollers on the side opposite from said suction box, a conduitconnected to said suction box for exhausing air from it whereby thestatic air pressure between said peripheries and said web is reduced toincrease the forceful contact between said supporting web and saidperipheries of said rollers as a result of the differential betweenatmospheric pressure on the portion of said web remote from said rollersand the reduced pressure on the portion of said web between theperipheries of said rollers to pull said webs in firm rotation-inducingcontact with said rollers irrespective of the weight of said web in ashallow curved indentation from said substantially linear path into thespace between said rollers whereby said web is firmly guided andretained in said substantially linear path irregardless of itsorientation.
 4. A roller support as set forth in claim 3 wherein sidemembers are attached to the sides of said suction box adjacent the endsof said rollers, and bearing and journal means rotatably connect theends of said rollers with said side members.